Solitary plasmacytoma of the thoracic vertebra presenting with sudden paraplegia and back pain: a pathologic case report.

Solitary plasmacytoma (SPC) accounts for 5% of plasma cell neoplasm. SPC of the spine is relatively rare, and SPC presenting with sudden paraplegia is very rare. A 53 year-old woman was admitted to our hospital complaining of sudden severe paraplegia and back pain. Emergency MRI revealed a tumor of the thoracic vertebra no. 10 (Th10). Pressure fracture of the Th10 was also recognized. The tumor was not osteolytic and invasion was recognized around the Th10. The tumor directly compressed the spinal cord. An excision of the tumor was performed under the clinical diagnosis of metastatic carcinoma. Pathologtically, the tumor consisted of plasmacytoid atypical cells with hyperchromatic nuclei. Histochemically, the tumor cells showed pyroninophilia. Immunohistochemically, the tumor cells were positive for λ-light chain, but negative for cytokeratin, epithelial mermbrane antigen, vimentin, CD45, CD20, CD45RO, κ-light chain, α-heavy chain, λ-heavy chain, μ-heavy chain, δ-heavy chain, ε-heavy chain, IgA, IgG, IgM, synaptophysin, chromogranin, S100 protein, desmin, α-smooth muscle antigen, myoglobin, and p53 protein. The Ki-67 labeling was 73%. The author diagnosed the tumor as SPC with λ-light chain disease. After the diagnosis, whole body CT and MRI revealed no other tumors. Blood and serum test revealed no significant changes; no M-protein was recognized. However, voided urine test revealed λ-light chain protein. The patient underwent fixation operation of TH10, and received radiation (50 Gray) and chemotherapy. No recurrence or transformation into myeloma occurred at the present time 25 months after the first manifestation. The present study indicated that pathological examination is an only clue to the diagnosis of SPC of the vertebra bone.